Funds requested in this application are for the continued support and operation of the Electron Microscope Service Laboratory in the Biological Laboratories, Harvard Universty. This grant has continued to support the activities of numerous undergraduate students, graduate students, postdoctoral fellows and members of the faculty in their research projects using electron microscopy. For these people the service laboratory is their sole access to an electron microscope. The primary functions of the facility are to 1) provide equipment and space for electron microscopical investigations by members of the department and 2) to provide instruction in specimen preparation, electron microscopy and evaluation of results to users of the laboratory. BIBLIOGRAPHIC REFERENCES: Kafatos, F.C., J. Regier, G.D. Mazur, M.R. Nadel, H. Blau, W.H. Petri, A.R. Wyman, R.E. Gelinas. P.B. Moore, M. Paul, A. Efstratiadis, J. Vournakis, M.R. Goldsmith, J. Hunsley, B. Baker and J. Nardi (1975). The eggshell of insects: Differentiation-specific proteins and the control of their synthesis and accumulation during development. In Biochemical Differentiation of Insect Glands, Vol. X of Results and Problems in Cell Differentiation (W. Beermann, ed.), Springer-Verlag, Berlin.